To conduct a multicenter longitudinal investigation of normative bone density, skeletal, and pubertal maturation data in children. Normative growth and bone density measurements will be obtained annually for three consecutive years. The children will undergo a yearly radiographic evaluation including DEXA and bone age x-ray and also an evaluation by a pediatric endocrinologist or nurse practitioner to determine pubertal status, height, weight, and BM!. Heights will be taken on a calibrated stadiometer and measured in triplicate to assure accuracy. Each clinical center will enter the growth and puberty data that they generate and transmit these data electronically to the data coordinating center. All of the radiology data (bone age and bone density studies) will be read centrally by a radiologist appointed by the data- coordinating center. Those data will be entered directly into the centralized database located at the coordinating center. On a monthly basis, the clinical centers will arrange for the supervision of the calibration of their bone density instruments. The clinical centers will conduct a pilot study on a total of 12 children to test the study procedures and instruments.